The conventional art is explained with respect to the example of a liquid-jet-type of X-ray-generating device. FIG. 4 is a cross-sectional view depicting one example of a conventional liquid-jet-type X-ray-generating device. The device of FIG. 4 comprises a light-source chamber 100. The light-source chamber 100 is provided with a vacuum pump 102 that evacuates the interior of the light-source chamber 100. A nozzle 101 is disposed inside the light-source chamber 100. The nozzle 101 is connected to a conduit 103, which is connected to a cylinder (not shown) containing a liquid-gas mixture. A support member 104 extends between the conduit 103 and the inner surface of the light-source chamber 100 to position the nozzle 101 and to prevent misalignment of the conduit 103.
The cylinder for the liquid-gas mixture is filled with a mixture of a target gas, such as xenon (Xe), and a liquid such as water. The liquid-gas mixture is fed from the cylinder to the nozzle 101 via the conduit 103, from which the liquid-gas mixture is sprayed from the tip of the nozzle 101 into the light-source chamber 100. This sprayed liquid-gas mixture forms the target material when generating a plasma.
A mirror (first mirror) 105 is attached via a mount 106 within the light-source chamber 100. The mirror 105 is an elliptical mirror having a reflecting surface 105a, which is bowl-shaped in the present example. The reflecting surface 105a of the mirror 105 is coated with a multilayer film, which in one example is made of alternating layers of Mo and Si. Among the X-rays radiated from the plasma, X-rays in the vicinity of a 13.4-nm wavelength are reflected by the reflecting surface 105a of the mirror 105, and form an X-ray beam. The X-ray beam is guided to a downstream optical system.
A flange member 110 is attached to an outer wall (upper right side in the figure) of the light-source chamber 100. A condenser mechanism 108, including a condenser lens 107, is attached to the outer surface of the flange member 110. A laser-light source 109 is disposed upstream (right side in the figure) of the condenser mechanism 108. The condenser lens 107 condenses laser light L emitted from the laser-light source 109 to the tip of the nozzle 101. A plasma P is produced by irradiating the spray of liquid-gas mixture with the condensed laser light L. X-rays radiate from the plasma P.
The condenser lens 107 and condenser mechanism 108 are attached to the outer surface of the flange member 110 principally because such a manner of mounting is easy from a manufacturing standpoint. The flange member 110 also serves as a sealing cover for a corresponding opening in the light-source chamber 100 used for removing components such as the mirror 105 from the chamber. The flange member 110 thus can be attached to and removed from the outer surface of the light-source chamber 100.
An opening 100a is formed in the lower surface of the light-source chamber 100, through which opening the X-ray beam passes. An X-ray-transmissive filter 111 is disposed inside the light-source chamber 100 at a position that covers the opening 100a. The X-ray-transmissive filter 111 is a thin film made of beryllium (Be) or the like and filters visible and ultraviolet light, also produced by the plasma, from the X-ray beam. An aperture plate 113 is disposed outside of the light-source chamber 100 directly below the X-ray-transmissive filter 111. The aperture plate 113 is a disc having a central pinhole 113a. The X-ray beam reflected by the mirror 105 passes through the pinhole 113a of the aperture plate 113 to the downstream optical system (not shown). Meanwhile, components surrounding the pinhole 113a of the aperture plate 113 block scattered X-rays (leaked light).
In the liquid-jet-type of X-ray-generating device described above, the liquid-gas mixture (target material) and the like form atoms and ionic particles during plasma generation. If these particles become adhered to or are deposited on the tip of the nozzle 101, then the liquid-gas mixture cannot spray normally from the nozzle. Alternatively, if these particles peripherally scatter and adhere to or are deposited on the reflecting surface 105a of the mirror 105, then the reflectance of the mirror 105 is decreased. These scattered particles also can adhere to or become deposited on the X-ray-transmissive filter 111. Consequently, the nozzle 101, the mirror 105, the X-ray-transmissive filter 111, and the like inside the light-source chamber 100 of the X-ray-generating device need to be replaced relatively frequently at fixed respective intervals, and hence are examples of “high-frequency-maintenance components.”
To replace high-frequency-maintenance components such as the nozzle 101, the mirror 105, and the X-ray-transmissive filter 111, the flange member 110 is detached from the light-source chamber 100, thereby forming an opening in the chamber wall. The light-source chamber 100 of the conventional device shown FIG. 4 has only one flange member 110. Thus, it is necessary to detach the flange member 110 to remove any of the components such as the nozzle 101, the mirror 105, and the X-ray-transmissive filter 111 for maintenance work. As noted above, for manufacturing simplicity, the condenser lens 107 and condenser mechanism 108 also are attached to the flange member 110. Accordingly, when replacing some or all the components (including any of various high-frequency-maintenance components) inside the light-source chamber 100, the condenser lens 107 and the condenser mechanism 108 (which may not need replacement) must first be detached from the flange member 110.
In the liquid-jet-type X-ray-generating device shown in FIG. 4, the high-frequency-maintenance component typically requiring the most frequent maintenance-related replacement is the nozzle 101. The mirror 105 and the X-ray-transmissive filter 111, also regarded as high-frequency-maintenance components, typically require less frequent replacement (the filter 111 typically requiring less frequent replacement than the mirror 105). In view of the depicted arrangement of these components as shown in FIG. 4, the mirror 105 must be detached first in order to replace the nozzle 101. Thus, each time the nozzle 101, having the highest replacement frequency, is replaced, the mirror 105, the condenser lens 107, and the condenser mechanism 108 (all having lower replacement frequencies) also must be detached and removed. Similarly, each time the X-ray-transmissive filter 111 is replaced, the nozzle 101, the mirror 105, the condenser lens 107, and the condenser mechanism 108 all must be detached and removed, too.
Thus, in a conventional X-ray-generating device, replacing certain components for maintenance and other purposes requires that other components not requiring as frequent replacement also be removed in order to detach the components requiring replacement, which makes replacement work complicated and troublesome. Furthermore, if the condenser lens 107 and the condenser mechanism 108 are detached every time replacement work is performed on another component, then the problem arises of having to realign the condenser lens 107 and the condenser mechanism 108 with each other and with the downstream optical system every time maintenance is performed.